1. Field of the Invention
This invention relates to the production of alcohol and relates particularly to the production of alcohol by reacting an aldehyde or an acetal with hydrogen.
2. Description of the Prior Art
The production of an alcohol by reacting an aldehyde with hydrogen is known. The hydrogen adds on to the carbonyl group of the aldehyde to form the hydroxyl group of the alcohol and the reaction is carried out in the presence of a hydrogenation catalyst. Catalysts employed for this purpose have been nickel, the nickel being deposited on kieselguhr, for example, or molybdenum sulfide. Rhodium and cobalt catalysts have also been used. Palladium or platinum deposited on carbon and rhodium deposited on charcoal are also known as catalysts for the hydrogenation of aldehydes. Reaction conditions have included pressures in the range of 2000-4000 pounds per square inch gage and temperatures in the range of 300.degree.-550.degree. F.
The production of an alcohol by reacting an acetal with hydrogen is also known.
In the prior art processes of reacting an aldehyde or an acetal with hydrogen to form an alcohol, various difficulties have been encountered. For example, the selectivity of the catalysts with respect to the reaction of the aldehyde or acetal with the hydrogen, as opposed to competing hydrogenation reactions, has not been all that could be desired. More specifically, where ketones have been in admixture with the aldehyde or acetal, an undesirable, large proportion of the ketones has reacted with the hydrogen in competition with the aldehyde or acetal. Further, more specifically, where the production of an unsaturated alcohol from an unsaturated aldehyde or acetal is desired, hydrogenation of the double bond competes with the hydrogenation of the carbonyl groups of the aldehyde or acetal with the result that an unsaturated alcohol is not formed. Moreover, hydrogenolysis of the hydroxyl group of the alcohol product can also occur to an undesired extent.
Another difficulty, with respect to various of the processes heretofore employed, is the tendency of the catalysts to lose activity to a greater or lesser extent in the presence of various impurities in the aldehyde or acetal feed. Thus, for example, rhodium deposited on charcoal is almost completely inhibited in its hydrogenation activity for aldehydes in the presence of carbon monoxide. A commercial source of aldehydes is the hydroformylation of olefins by reacting the olefins with carbon monoxide and hydrogen in the presence of a catalyst. Accordingly, where the aldehyde feed has been obtained by hydroformylation of olefins, rigorous cleanup procedures are required to remove traces of carbon monoxide from the feed in order to prevent catalyst deactivation. Further, for example, various of the catalysts heretofore employed are deactivated by dienes and sulfur in the feed and, where such catalysts have been employed, purification of a feed containing such compounds has been required.